External fixation device and fixation device set

ABSTRACT

A fixation device set S includes an external fixation device  10  which is attached on one end-side of first and second pins P 1 , P 2 ; and a pin fixture  100  which is attached on the other end-side thereof. The external fixation device  10  includes a first and a second permanent magnets  32, 34  disposed with their same poles opposed to each other; a first holding portion  14  provided in the first permanent magnet  34 ; a second holding portion  36  provided in the second permanent magnet  34 ; first limiter portions  16   a,    16   b  sandwiching the first and the second permanent magnets  32, 34  from a second direction; and second limiter portions  66  connecting the first limiter portions  16   a,    16   b  to each other. The first pins P 1  are inserted through through-holes  20  in the first holding portion  14 , whereas the second holding portion  36  is attached to the second pin P 2  via a ball joint  50.

TECHNICAL FIELD

The present invention relates to external fixation devices and fixationdevice sets, and more specifically to an external fixation device and afixation device set used in treating articular cartilage damage.

BACKGROUND ART

Extensive articular cartilage damage is treated typically by making asmall hole in the damaged area using a drill, or an awl to stimulatebleeding from bone marrow thereby introducing bone marrow mesenchymalcells into the joint. Applying a load, however, to the damaged part soonafter the operation poses a risk of damaging still immature tissues.

Patent Literature 1 discloses an example of an external fixation devicewhich can be utilized in such a treatment of an articular cartilagedamage. The external fixation device includes ball joints and a gearbox, sandwiches the joint and mechanically fixes two sides of the jointin order to protect the damaged part, so that joint bone parts areseparated from each other and the damaged part will have a reduced load.Then, with the external fixation device attached, the patient moves thejoint.

CITATION LIST Patent Literature

Patent Literature 1: JP-A 2002-345837

Patent Literature 2: JP-A 2005-245470

SUMMARY OF INVENTION Technical Problem

However, the external, fixation device disclosed in Patent Literature 1includes a large number of parts and has a complicated structure.

Patent Literature 2 discloses an external fixation device which includesa magnet. However, in this external fixation device, a pair of magneticbodies, one of which fixed to a first bone portion and the other fixedto a second bone portion, contract to each other when the device isused, and cannot be utilized in treating an articular cartilage damagewhere the first bone portion and the second bone portion in a joint mustbe separated from each other.

Therefore, a primary object of the present invention is to provide anexternal fixation device which includes a decreased number of parts andhas a simple structure yet is capable of separating a first bone portionand a second bone portion from each other in a joint thereby makingpossible to effectively treating the articular cartilage damage; and toprovide a fixation device set.

Solution to Problem

According to an aspect of the present invention, there is provided anexternal fixation device for keeping a first bone portion and a secondbone portion separated from each other in a joint, by attaching to afirst pin which penetrates the first bone portion and to a second pinwhich penetrates the second bone portion. The device includes a firstpermanent magnet and a second permanent magnet which are opposed to eachother, with their same poles facing each other; a first holding portionwhich is disposed on a surface of the first permanent magnet, on a sidefacing away from a surface opposing to the second permanent magnet, andis attached to the first pin; a second holding portion which is disposedon a surface of the second permanent magnet, on a side facing away froma surface opposing to the first permanent magnet, and is attached to thesecond pin; and a pair of first limiter portions which allow movement ofthe first permanent magnet and the second permanent magnet in a firstdirection defined as a direction of their repulsion force by sandwichingthe first permanent magnet and the second permanent magnet from a seconddirection defined as a direction perpendicular to the first direction,and limit movement thereof in the second direction.

In the present invention, the first permanent magnet and the secondpermanent magnet are disposed with their same poles opposed to eachother, and a pair of first limiter portions sandwich the first permanentmagnet and the second permanent magnet. Therefore, the first permanentmagnet and the second permanent magnet repulse against each other,moving away from each other in the direction of the repulsion force,i.e., in the first direction. As a result, the first pin which isconnected to the first permanent magnet via the first holding portion,and the second pin which is connected to the second permanent magnet viathe second holding portion, move away from each other. This makes itpossible to move a joint, with its first bone portion and second boneportion kept apart from each other, i.e., with the cartilage part of thecleft between articulations kept open. By utilizing the repulsion forcebetween the first permanent magnet and the second permanent magnet asdescribed above, it becomes possible to reduce the number of parts andsimplify the structure, and therefore, it becomes possible to reduce aload to the damaged area of the articular cartilage (cartilage partunder regeneration) and to effectively treat the articular cartilagedamage. In other words, it becomes possible to obtain an externalfixation device which includes a decreased number of parts and has asimple structure yet is capable of effectively treating the articularcartilage damage.

Preferably, the external fixation device further includes a secondlimiter portion disposed to connect the pair of first limiter portionsto each other to limit movement of the first permanent magnet and thesecond permanent magnet in a third direction defined as a directionperpendicular to both of the first direction and the second direction.In this case, it becomes possible to limit movement of the firstpermanent magnet and the second permanent magnet in the third directionwhich is the direction perpendicular to both of the first direction andthe second direction. This prevents the first permanent magnet and thesecond permanent magnet from becoming twisted to each other, therebyproviding a smoother linear reciprocating relative movement between thefirst permanent magnet and the second permanent magnet.

Further preferably, the second limiter portion includes a magneticmember. In this case, the arrangement makes it possible to reduce aleakage magnetic field around the external fixation device. Therefore,the arrangement makes it possible to reduce adverse effect to thesurrounds.

Further, preferably, the external fixation device includes a ball jointfor attaching at least one of the first holding portion and the secondholding portion to a corresponding one of the first pin and the secondpin. In this case, at least one of the first holding portion and thesecond holding portion is attached to the corresponding pin(s) via theball joint. Therefore, the arrangement allows simultaneous, relativestretching/contracting and pivoting movements between components on thefirst holding portion side and those on the second holding portion sideof the external fixation device. Hence, the external fixation device iscapable of following bending and stretching or pivoting movements of thejoint, and the patient can move the joint freely. As a result, the jointcan be moved smoothly, with a further reduced load onto the articularcartilage damage area (cartilage part under regeneration), making itpossible to treat extensive articular cartilage damage more effectively.

Preferably, the second holding portion is connected to the ball joint,whereas, the first holding portion has a through-hole for insertion ofthe first pin. In this case, the first holding portion can be attachedeasily to the first pin by inserting the first pin through thethrough-hole of the first holding portion, and by attaching the secondholding portion to the second pin via the ball joint, the joint can bemoved smoothly.

Further preferably, at least one of the first holding portion and thesecond holding portion has a through-hole for insertion of thecorresponding one of the first pin and the second pin. In this case, byinserting a corresponding pin(s), through the through-hole(s) of atleast one of the first holding portion and the second holding portion,the holding portion is attached easily to the pin.

Further, preferably, the external fixation device includes a slantedsleeve fitted into the through-hole. In this case, by fitting theslanted sleeve into the through-hole of the holding portion, the pinwhich penetrates the through-hole is oriented in a slanted direction.Therefore, it is possible to insert the pin into an area of the boneportion which has a high density of bone, depending on specificconditions of individual patients.

Preferably, the pair of first limiter portions and the first holdingportion are integral with each other. In this case, the arrangementfurther reduces the number of parts in the external fixation device.

Further preferably, each of the first permanent magnet and the secondpermanent magnet is rectangular parallelepiped. In this case, it ispossible to obtain a large repulsion force with a simple shape atreduced cost.

According to another aspect of the present invention, there is provideda fixation device set which includes the above-described externalfixation device for attaching to the first pin and the second pin ontheir common one end-side; and a pin fixture for attaching to the firstpin and the second pin on their common another end-side. The pin fixtureincludes a fixture main body; a first connecting portion for connectingthe fixture main body to the first pin; and a second connecting portionfor connecting the fixture main body to the second pin.

According to the present invention, the external fixation device isattached to a common one end-side of the first pin which penetrates thefirst bone portion and the second pin which penetrates the second boneportion, whereas the pin fixture is attached to the other commonend-side of the first pin and the second pin. The arrangement reducesunnecessary movement of the first pin and the second pin, therebyreducing damage to the bone portions. This works effectively, especiallyfor patients having a low density of bone. As described, it becomespossible to obtain the fixation device set which includes a decreasednumber of parts and has a simple structure yet is capable effectivelytreating the articular cartilage damage.

Preferably, the first connecting portion is pivotable with respect tothe fixture main body, whereas the second connecting portion is linearlymovable with respect to the fixture main body. In this case, therefore,even if there happens to be variations in the position of the first pinand the second pin on the pin fixture side as viewed from the joint, itis possible to allow for such variations and keep holding the otherend-side of the first pin and the second pin.

The above-described object and other objects, characteristics, aspectsand advantages of the present invention will become clearer from thefollowing detailed description of embodiments of the present inventionto be made with reference to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1( a) is a front view showing an external fixation device accordingto an embodiment of the present invention, whereas FIG. 1( b) is a sideview thereof.

FIG. 2( a) is a front view showing the external fixation device in FIG.1 with its second limiter portions removed, whereas FIG. 2( b) is a sideview thereof.

FIG. 3( a) is a front view showing a frame portion, FIG. 3( b) is a planview thereof, and FIG. 3( c) is a side view thereof.

FIG. 4( a) is a plan view showing a platy member, whereas FIG. 4( b) isa front view thereof.

FIG. 5( a) is a plan view showing a first support member, whereas FIG.5( b) is a front view thereof.

FIG. 6( a) is a plan view showing a second support member, FIG. 6( b) isa front view thereof, and FIG. 6( c) is a bottom view thereof.

FIG. 7( a) is a front view showing a first shaft portion, FIG. 7( b) isa plan view thereof, and FIG. 7( c) is a side thereof.

FIG. 8( a) is a front view showing a second shaft portion, whereas FIG.8( b) is a side view thereof.

FIG. 9( a) is a front view showing a first platy portion, whereas FIG.9( b) is a bottom view thereof.

FIG. 10( a) is a front view showing a second platy portion, whereas FIG.10( b) is a bottom view thereof.

FIG. 11( a) is a front view showing an example of a pin fixture, whereasFIG. 11( b) is a side view thereof.

FIG. 12( a) is a front view showing a fixture main body, FIG. 12( b) isa side view thereof, FIG. 12( c) is a bottom view thereof, and FIG. 12(d) is a perspective view thereof.

FIG. 13( a) is a front view showing a first connecting portion, FIG. 13(b) is a bottom view thereof, and FIG. 13( c) is a side view thereof.

FIG. 14( a) is a front view showing a second connecting portion, FIG.14( b) is a bottom view thereof, and FIG. 14( c) is a side view thereof.

FIG. 15 is an illustrative drawing showing a fixation device set, withan external fixation device attached on one side of a knee joint, and apin fixture attached to the other side thereof.

FIG. 16 is an illustrative drawing showing a knee joint and the externalfixation device when the knee is bent: FIG. 16( a) shows a state wherethe knee is not bent, FIG. 16( b) shows a state where the knee is bentto 90°, and FIG. 16( c) shows a state where the knee is bent to a 120°.

FIG. 17( a) is a front view showing an external fixation deviceaccording to another embodiment of the present invention, whereas FIG.17( b) is a side view thereof.

FIG. 18 (a) is a front view showing a slanted sleeve, whereas FIG. 18(b) is a side view thereof.

FIG. 19 is an illustrative drawing showing a state where the externalfixation devices are attached on both sides of a knee joint.

FIG. 20 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 21 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 22 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 23 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 24 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 25 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 26 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 27 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 28 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 29 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 30 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 31 is a front view showing an external fixation device according tostill another embodiment of the present invention.

FIG. 32 is an illustrative drawing showing another example of thestopper.

FIG. 33 is an illustrative drawing showing another example of the pin.

FIG. 34 is an illustrative drawing showing another example of the pin.

FIG. 35 is a side view showing another example of the sleeve.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

Referring to FIG. 1 through FIG. 3, FIG. 17, and FIG. 20 through FIG.31, in the embodiments of the present invention, a direction indicatedby Arrow X, i.e., a direction of a repulsion force acting between afirst permanent magnet and a second permanent magnet is the firstdirection; a direction indicated by Arrow Y, i.e., a directionperpendicular to Arrow X direction is the second direction; and adirection indicated by Arrow Z, i.e., a direction perpendicular to bothof the directions indicated by Arrows X and Y is the third direction.

Referring to FIG. 1 through FIG. 3, an external fixation device 10includes a frame portion 12. The frame portion 12 opens in the firstdirection and the third direction, is substantially U-shaped, ismagnetic, and preferably made of a ferrous material or a magneticstainless steel such as SS400. The frame portion 12 includes a prismaticfirst holding portion 14; a pair of first limiter portions 16 a, 16 bwhich are substantially plate-like and extend from two ends of the firstholding portion 14 in a substantially perpendicular direction withrespect to the first holding portion 14; and stopper portions 18 a, 18 bformed at tips of the pair of first limiter portions 16 a, 16 brespectively. The first holding portion 14 has a plurality (two, in thepresent embodiment) of through-holes 20 extending in the thirddirection. The through-holes 20 will be penetrated by first pins P1 (tobe described later). The frame portion 12 also has, in its two surfaceswhich are perpendicular to the third direction, a plurality (five ineach surface, in the present embodiment) of screw holes 22 extending inthe third direction. Further, each of the stopper portions 18 a, 18 bhas a screw hole 24 penetrating in the first direction.

The first limiter portions 16 a, 16 b of the frame portion 12 sandwich afirst permanent magnet 32 and a second permanent magnet 34 (both will bedescribed later) from the second direction so as to allow the firstpermanent magnet 32 and the second permanent magnet 34 to move in thefirst direction but limit them in movement in the second direction.

As shown in FIG. 3, the first limiter portions 16 a, 16 b have theirinner surfaces formed with recesses 26 a, 26 b respectively. Referringto FIG. 2, the recess 26 a is fitted with a platy member 28, which isshown in FIG. 4, is substantially plate-like, and flush with the firstlimiter portion 16 a, whereas the recess 26 b is fitted with anotherplaty member 28 flush with the first limiter portion 16 b. The platymembers 28 are nonmagnetic, preferably being formed of a nonmagneticstainless steel such as SUS304, aluminum, titanium, etc. The platymembers 28 prevent magnetic short-circuit between the first permanentmagnet 32 and the second permanent magnet 34.

The first holding portion 14 of the frame portion 12 has an innersurface 30, to which the first permanent magnet 32 is attached. In otherwords, the first holding portion 14 is on a surface away from anopposing surface 32 a of the first permanent magnet 32. Between thefirst limiter portions 16 a, 16 b of the frame portion 12, there isdisposed the second permanent magnet 34 to oppose to the first permanentmagnet 32. The first permanent magnet 32 and the second permanent magnet34 have the same shape of a generally rectangular parallelepiped, andare disposed so that their same poles oppose to each other. As shown inFIG. 2, in the present embodiment, the first permanent magnet 32 has itsN pole on the opposing surface 32 a side, and its S pole on the sideaway from the opposing surface 32 a (the first holding portion 14 side).Likewise, the second permanent magnet 34 has its N pole on its opposingsurface 34 a side, and its S pole on the side away from the opposingsurface 34 a (on the side facing a second holding portion 36 (which willbe described later)). The first permanent magnet 32 and the secondpermanent magnet 34 are provided preferably by an R—Fe—B sintered magnet(R represents a rare-earth element).

The second holding portion 36 is on a surface away from the opposingsurface 34 a of the second permanent magnet 34. The second holdingportion 36 includes a strip-shaped first support member 38 as shown inFIG. 5, and two second support members 40 as split halves as shown inFIG. 6. The first support member 38 has a hemispherical recess 42, and aplurality (eight, in the present embodiment) of screw holes 44. Thesecond support member 40 has a semicircular recess 46, and a plurality(four, in the present embodiment) of screw holes 48 as through holes.The first support member 38 and the second support members 40 aremagnetic, formed preferably of a ferrous material or a magneticstainless steel such as SS400.

As shown in FIG. 1 and FIG. 2, the second holding portion 36 isconnected to a ball joint 50. The ball joint 50 includes a first shaftportion 52 and a second shaft portion 54. Referring to FIG. 7, the firstshaft portion 52 has a ball portion 56 and a female-threaded portion 58.Referring to FIG. 8, the second shaft portion 54 has a tube-like portion62 which has a through-hole 60; and a male-threaded portion 64. Thefirst shaft portion 52 and the second shaft portion 54 are nonmagnetic,preferably being formed of a nonmagnetic stainless steel such as SUS304,aluminum, titanium, etc. The through-hole 60 will be penetrated by asecond pin P2 (to be described later). As the male-threaded portion 64is threaded into the female-threaded portion 58, the ball joint 50 iscompleted as an assembly. The ball portion 56 of the ball joint 50 isinserted into the recess 42 in the first support member 38 of the secondholding portion 36, and then the first support member 38 and the twosecond support members 40 are assembled together to surround an exposedregion of the ball portion 56 with two recesses 46. Under this state,screws (not illustrated) are threaded into the screw holes 48, 44.

Returning to FIG. 1, two second limiter portions 66 are disposed tocover two openings of the frame portion 12 opening in the thirddirection. In other words, in order to limit the first permanent magnet32 and the second permanent magnet 34 from moving in the thirddirection, the two second limiter portions 66 are placed, connecting thepair of first limiter portions 16 a, 16 b to each other. Each secondlimiter portion 66 includes a first platy portion 68 and a second platyportion 70. Referring to FIG. 9 and FIG. 10, the first platy portion 68and the second platy portion 70 have substantially the same shape exceptfor their thicknesses. The first platy portion 68 has a cutout 72; aplurality (two, in the present embodiment 2) of through-holes 74; and aplurality (five, in the present embodiment) of screw holes 76 asthrough-holes. The first platy portion 68 is nonmagnetic, preferablybeing formed of a nonmagnetic stainless steel such as SUS304, aluminum,titanium, etc. The second platy portion 70 has a cutout 78; a plurality(two, in the present embodiment) of through-holes 80; and a plurality(five, in the present embodiment) of screw holes 82 as through-holes.The second platy portion 70 is magnetic, and preferably formed of aferrous material such as SS400, or a magnetic stainless steel.

The frame portion 12 is sandwiched from the third direction by the twofirst platy portions 68 to cover two openings of the frame portion 12opening in the third direction; the second platy portions 70 are placedon the respective first platy portions 68; and then screws 84 (seeFIG. 1) are threaded into the screw holes 82, 76, 22, whereby the firstplaty portions 68 and the second platy portions 70 are attached to theframe portion 12.

Referring to FIG. 2, according to the external fixation device 10 asdescribed, the second permanent magnet 34, and therefore the ball joint50, is movable linearly in a reciprocating fashion in the firstdirection, whereas the ball joint 50 is pivotable (for example, in ArrowT direction) around the ball portion 56 with respect to the secondholding portion 36. Thus, when the external fixation device 10 isattached to a joint via the first pins P1 and the second pin P2, theexternal fixation device 10 can allow the joint to move in a directionin which the first pins P1 become twisted with respect to the second pinP2.

Returning to FIG. 1 and FIG. 3, until the external fixation device 10 asdescribed thus far is attached to a joint, set screws 86 which arethreaded into the two screw holes 24 keep the second holding portion 36and the second permanent magnet 34 pressed toward the first permanentmagnet 32.

Next, the pin fixture 100 will be described with reference to FIG. 11through FIG. 14.

As shown in FIG. 11, the pin fixture 100 includes a fixture main body102; a first connecting portion 104 which connect the fixture main body102 and the first pin P1 (see FIG. 15) to each other; and a secondconnecting portion 106 which connects the fixture main body 102 and thesecond pin P2 (see FIG. 15) to each other. The fixture main body 102,the first connecting portion 104 and the second connecting portion 106are nonmagnetic, preferably being formed of a nonmagnetic stainlesssteel such as SUS304, aluminum, titanium, etc.

As shown in FIG. 12, the fixture main body 102 is substantially J-shapedin a front view (see FIG. 12( a)), and includes a thick portion 108, andtwo thin portions 110, 112. The thin portion 110 is obtained by forminga recess 114 in the fixture main body 102. The thin portion 112 isobtained by forming a recess 116 opening in one direction in the fixturemain body 102. The thick portion 108 is formed with a through-hole 118,the thin portion 110 is formed with a screw hole 120 as a through-hole,and the thin portion 112 is formed with a screw hole 122 as athrough-hole.

As shown in FIG. 13, the first connecting portion 104 is substantiallyI-shaped in a front view (see FIG. 13( a)), and includes a thick portion124 and a thin portion 126. The thick portion 124 is formed with athrough-hole 128, whereas the thin portion 126 is formed with athrough-hole 130 as a long hole.

As shown in FIG. 14, the second connecting portion 106 is substantiallyI-shaped in a front view (see FIG. 14( a)), and includes a thick portion132 and a thin portion 134. The thick portion 132 is formed with athrough-hole 136, whereas the thin portion 134 is formed with athrough-hole 138 as a long hole.

Referring to FIG. 11 through FIG. 13, the screw hole 120 of the fixturemain body 102 and the through-hole 130 of the first connecting portion104 align with each other when the thin portion 126 of the firstconnecting portion 104 is disposed in the recess 114 of the fixture mainbody 102, and under this state a bolt 140 is inserted through thethrough-hole 130 and threaded into the screw hole 120. Being attached asdescribed, the first connecting portion 104 is pivotable in a directionindicated by Arrow T1 within an angle range of approximately 140 degreesand is linearly movable in a direction indicated by Arrow Y1, withrespect to the fixture main body 102. In regard of the pivotal movementof the first connecting portion 104, it is acceptable in actual use,that as far as the first connecting portion 104 is pivotable withrespect to the fixture main body 102 within a ± approximately 25-degreerange from a position indicated by solid lines in FIG. 11( a). Further,referring to FIG. 14, the screw hole 122 of the fixture main body 102and the through-hole 138 of the second connecting portion 106 align witheach other when the thin portion 134 of the second connecting portion106 is fitted into the recess 116 of the fixture main body 102, andunder this state a washer 142 is placed in between, a bolt 144 isinserted through the through-hole 138, and threaded into the screw hole122. Being attached as described, the second connecting portion 106 islinearly movable with respect to the fixture main body 102 in adirection indicated by Arrow X1.

Referring to FIG. 15, a fixation device set S which includes theexternal fixation device 10 and the pin fixture 100 is attached to ajoint as follows: Herein, description will be made for a case where afirst bone portion B on a lower-leg portion side and a second boneportion C on a thigh side are separated from each other, and under thiscondition, the external fixation device 10 and the pin fixture 100 areattached to a knee joint A to sandwich the knee joint in between so thatthe external fixation device 10 is on one side of the first bone portionB and the second bone portion C, whereas the pin fixture 100 is on theother side of the first bone portion B and the second bone portion C.

First, by means of a drill for example, two through-holes are made inthe first bone portion B, and one through-hole as well, in the secondbone portion C. Next, the first pins P1 are inserted through thethrough-holes made in the first bone portion B respectively, whereas thesecond pin P2 is inserted through the through-hole made in the secondbone portion C. It is preferable that each of the first pins P1 and thesecond pin P2 is formed in a rod-like shape, using a material containingtitanium which has superb biocompatibility. In the present embodiment,each of the first pins P1 and the second pin P2 has their two endportions formed with a male-thread on their outer surface. FIG. 15 showsonly one of the two first pins P1.

Then, three nuts 146, the external, fixation device 10 shown in FIG. 1,and three nuts 146 are attached in this order to the three pins (twofirst pins P1 and one second pin P2) on one side as viewed from the kneejoint A. In other words, on one side as viewed from the knee joint A, anut 146 is advanced along each of the two first pins P1 and one secondpin P2, to an inner side (side closer to the knee joint A); each of thefirst pins P1 is inserted through corresponding through-holes(through-holes 20, 74, 80) of the external fixation device 10, while thesecond pin P2 is inserted through the through-hole 60 in the ball joint50 of the external fixation device 10, whereby the external fixationdevice 10 is inserted around the three pins; and further, a nut 146 isinserted around each of the two first pins P1 and the second pin P2.Hence, the external fixation device 10 is attached to the two first pinsP1 and one second pin P2, being sandwiched from two sides by three nuts146 each on each side. Under this state, the external fixation device 10is held so as not to come out of the first pins P1 and the second pinP2. Each of the first pins P1 and the second pin P2 is rotatable withrespect to the external fixation device 10. However, the first pins P1may be non-rotatable with respect to the external fixation device 10.

Thereafter, as shown in FIG. 1, the two set screws 86 which keep thesecond holding portion 36 and the second permanent magnet 34 pressedtoward the first permanent magnet 32 are released or removed, asnecessary, from the external fixation device 10. As a result, due to arepulsion force acting between the first permanent magnet 32 and thesecond permanent magnet 34, a force works in a direction to increase adistance between the first pins P1 and the second pin P2.

This expansion/contraction movement of the external fixation device 10is observed, to determine if the pin fixture 100 should be attached,another external fixation device 10 should be attached, or nothingshould be made, on the other side as viewed from the knee joint A.

In the present description, the pin fixture 100 will be attached.

The pin fixture 100 is attached in the same way as the external fixationdevice 10.

First, three nuts 146, the pin fixture 100 shown in FIG. 11, and threenuts 146 are attached in this order to the three pins (two first pins P1and one second pin P2) on the other side as viewed from the knee jointA. In other words, on the other side as viewed from the knee joint A, anut 146 is advanced along each of the two first pins P1 and one secondpin P2, to an inner side (side closer to the knee joint A); each of thefirst pins P1 is inserted through a corresponding one of thethrough-holes 118, 128 of the pin fixture 100 while the second pin P2 isinserted through the through-hole 136 in the pin fixture 100, wherebythe pin fixture 100 is inserted around the three pins; and further, anut 146 is inserted around each of the two first pins P1 and the secondpin P2. Hence, the pin fixture 100 is attached to the two first pins P1and one second pin P2, being sandwiched from two sides by three nuts 146each on each side. Under this state, the pin fixture 100 is held so asnot to come out of the first pins P1 and the second pin P2. Each of thefirst pins P1 and the second pin P2 is rotatable with respect to the pinfixture 100. However, the first pins P1 may be non-rotatable withrespect to the pin fixture 100.

In the external fixation device 10 attached to the knee joint A, whenthe patient is standing upright for example, a repulsion force ofapproximately 240N (24.5 kgf) is acting between the first permanentmagnet 32 and the second permanent magnet 34.

Description will be made for a case where a knee is being bent with theexternal fixation device 10 and the pin fixture 100 attached thereto asdescribed above, with reference to FIG. 16( a) through FIG. 16( c).

As shown in FIG. 16( a), when the knee is not bent, the first permanentmagnet 32 and the second permanent magnet 34 are close to each other.Next, when the knee is bent at approximately 90° as shown in FIG. 16(b), the second permanent magnet 34 moves away from the first permanentmagnet 32. Then, when the knee is bent at approximately 120° as shown inFIG. 16( c), the second permanent magnet 34 moves further away from thefirst permanent magnet 32. While the knee is being bent from 0°(stretched state) to 120°, the ball joint 50 pivots around the ballportion 56 with respect to the second holding portion 36. As described,the first bone portion B and the second bone portion C are kept apartfrom each other when the knee is bent.

According to the external fixation device 10, the first permanent magnet32 and the second permanent magnet 34 are disposed so that their samepoles oppose to each other, and the first permanent magnet 32 and thesecond permanent magnet 34 are sandwiched between the pair of firstlimiter portions 16 a, 16 b. Therefore, the first permanent magnet 32and the second permanent magnet 34 repulse against each other, movingaway from each other in the direction of the repulsion force, i.e., inthe first direction. As a result, the first pins P1 which are connectedto the first permanent magnet 32 via the first holding portion 14, andthe second pin P2 which is connected to the second permanent magnet 34via the second holding portion 36 move away from each other, making itpossible to move the knee joint A while the first bone portion B and thesecond bone portion C are kept apart from each other, i.e., with thecartilage part of the knee joint A kept open. By utilizing the repulsionforce between the first permanent magnet 32 and the second permanentmagnet 34 as described above, it becomes possible to reduce the numberof parts and simplify the structure, and therefore, it becomes possibleto reduce a load to the damaged area of the articular cartilage(cartilage part under regeneration) and to effectively treat thearticular cartilage damage. In other words, it becomes possible toobtain the external fixation device 10 which includes a decreased numberof parts and has a simple structure yet is capable of effectivelytreating the articular cartilage damage. Since the external fixationdevice 10 can be made at a low cost, made smaller and more compactlythan conventional ones, it can reduce burdens on the patient in dailylife.

By providing two second limiter portions 66 to connect the pair of firstlimiter portions 16 a, 16 b to each other, it becomes possible to limitmovement of the second permanent magnet 34 in the third direction whichis the direction perpendicular to both of the first direction and thesecond direction, preventing the first permanent magnet 32 and thesecond permanent magnet 34 from becoming twisted to each other, therebyproviding a smoother linear reciprocating movement of the secondpermanent magnet 34 relative to the first permanent magnet 32. Since thefirst permanent magnet 32 and the second permanent magnet 34 stay insidea space surrounded by the frame portion 12 and the second limiterportions 66, neither the first permanent magnet 32 nor the secondpermanent magnet 34 will rub against or pinch the patient's skin.

The second limiter portions 66 include the second platy portions 70which are magnetic. This reduces a leakage magnetic field around theexternal fixation device 10. Therefore the arrangement reduces adverseeffect to the surrounds.

The second holding portion 36 is attached to the second pin P2 via theball joint 50. This allows simultaneous, relative stretching/contracting(linear) and pivoting movements between components on the first holdingportion 14 side and those on the second holding portion 36 side of theexternal fixation device 10. Therefore, the external fixation device 10is capable of following bending/stretching or pivoting movements of theknee joint A, and the patient can move the knee joint A freely. As aresult, the knee joint A can be moved smoothly, with a further reducedload onto the articular cartilage damage area (cartilage part underregeneration), making it possible to treat extensive articular cartilagedamage more effectively.

The arrangement that the first pins P1 are inserted through thethrough-holes 20 in the first holding portion 14 makes it easy to attachthe first holding portion 14 to the first pins P1.

The pair of first limiter portions 16 a, 16 b and the first holdingportion 14 are formed integrally with each other. This further reducesthe number of parts of the external fixation device 10.

Each of the first permanent magnet 32 and the second permanent magnet 34is rectangular parallelepiped, so a large repulsion force can beobtained with a simple shape at reduced cost.

The second pin P2 is rotatable with respect to the external fixationdevice 10. This makes it possible to move the knee joint A more freely.

The first bone portion B is penetrated by the first pins P1 and thesecond bone portion C is penetrated by the second pin P2, and theexternal fixation device 10 is attached on one end-side of the firstpins P1 and the second pin P2, whereas the pin fixture 100 is attachedon the other end-side thereof. This reduces unnecessary movement of thefirst pins P1 and the second pin P2, thereby reducing damage to thefirst bone portion B and the second bone portion C. This workseffectively, especially for patients having a low density of bone. Asdescribed, it becomes possible to obtain the fixation device set S whichincludes a decreased number of parts and has a simple structure yet iscapable effectively treating the articular cartilage damage.

FIG. 17 shows an external fixation device 10 a according to anotherembodiment.

The external fixation device 10 a has an attachable/detachable slantedsleeve 148. Also, the external fixation device 10 a has a frame portion12 a, which has the through-hole 20 and a through-hole 20 a having agreater diameter than the diameter of the through-hole 20, asthrough-holes for insertion of the first pins P1. Accordingly, the firstplaty portion 68 a of the second limiter portion 66 a have thethrough-hole 74 and a through-hole 74 a which has a greater diameterthan the diameter of the through-hole 74, whereas the second platyportion 70 a of the second limiter portion 66 a has the through-hole 80and a through-hole 80 a which has a greater diameter than the diameterof the through-hole 80. The external fixation device 10 a hasthrough-holes 20, 74 and 80, each having the same diameter as therespective diameter of the through-holes 20, 74 and 80 in the externalfixation device 10. Specifically, using FIG. 17( a) as an example, thethrough-holes 20 a, 74 a and 80 a are on the left side, whereas thethrough-holes 20, 74 and 80 are on the right side.

Referring to FIG. 18, the slanted sleeve 148 has a cylindrical portion150, and an annular flange portion 152 formed at an end of thecylindrical portion 150. The cylindrical portion 150 and the flangeportion 152 are formed with a through-hole 154 which extends in adirection slightly slanted with respect to an axis of the cylindricalportion 150 and flange portion 152. The slanted sleeve 148 as describedis fitted into the through-holes 80 a of the second platy portions 70 a,the through-holes 74 a of the first platy portions 68 a, and thethrough-hole 20 a of the frame portion 12 a. The through-hole 154 willbe penetrated by the first pin P1. The slanted sleeve 148 isnonmagnetic, preferably being formed of a nonmagnetic stainless steelsuch as SUS304, aluminum, titanium, etc. Other arrangements are the sameas in the external fixation device 10, so description therefor will notbe repeated.

According to the external fixation device 10 a as described, the slantedsleeve 148 is fitted into the through-holes 80 a, 74 a and 20 a, andtherefore it is possible to orient the first pin P1 which is insertedthrough the through-hole 154 in a slanted direction. This means that itis possible to insert the first pin P1 into an area of the first boneportion B which has a high density of bone, depending on specificconditions of individual patients.

The first connecting portions 104 is pivotable with respect to thefixture main body 102, and the second connecting portion 106 is linearlymovable with respect to the fixture main body 102. Therefore, even ifthere happens to be variations in the position of the first pins P1 andthe second pin P2 on the pin fixture 100 side as viewed from the kneejoint A, it is possible to allow for such variations and keep holdingthe other end-side of the first pins P1 and the second pin P2.

As shown in FIG. 19, there may be an arrangement where the pin fixture100 is not used, and two of the external fixation devices 10 areattached on two sides of the knee joint A. In this case, it is notnecessary to prepare the pin fixture 100.

Like an external fixation device 10 b shown in FIG. 20, a firstpermanent magnet 32 b and a second permanent magnet 34 b may be disposedin such a fashion that their N poles oppose to each other and their Spoles oppose to each other. Other arrangements are the same as in theexternal fixation device 10, so description therefor will not berepeated. It should be noted here that in FIG. 20 and thereafter, whenan external fixation device is shown, the second limiter portions willnot be described in order to avoid complication of the drawing. However,the second limiter portions are included, with appropriate modificationsmade thereto in accordance with the corresponding external fixationdevice.

The external fixation device 10 b as described provides the sameadvantages as offered by the external fixation device 10.

Like an external fixation device 10 c shown in FIG. 21, a ball joint 50a which is longer than the ball joint 50 by, e.g., 30 mm, may beutilized to fit for patients of specific body sizes. The ball joint 50 ahas its second shaft portion 54 a has a tube-like portion 62 a which hasthe through-hole 60; a leg portion 62 b which extends from the tube-likeportion 62 a; and the male-threaded portion 64. Other arrangements arethe same as in the external fixation device 10, so description thereforwill not be repeated.

According to the external fixation device 10 c as described, it ispossible to treat tall patients, for example, even if a large gap mustbe provided between a position to attach the first pins P1 and aposition to attach the second pin P2 in the knee joint A.

Like an external fixation device 10 d shown in FIG. 22, there may be anarrangement where a frame portion 12 d is not only formed with twothrough-holes 20 d but also have a ball joint 50 attached thereto. Inthis case, the frame portion 12 d includes a substantially U-shapedframe main body 156, and two support members 158 as split halves. Theframe main body 156 has a hemispherical recess 156 a, whereas thesupport member 158 has a semicircular recess 158 a. The ball portion 56of the ball joint 50 is inserted into the recess 156 a in the frame mainbody 156, and then the frame main body 156 and the two support members158 are assembled together to surround an exposed region of the ballportion 56 with the two recesses 158 a. Under this state, the frame mainbody 156 and the two support members 158 are integrally assembled withunillustrated fasteners. Two surfaces of the frame portion 12 d whichare perpendicular to the third direction are formed with eight (four ineach surface) screw holes 22. Other arrangements are the same as in theexternal fixation device 10, so description therefor will not berepeated.

According to the external fixation device 10 d as described, since theframe portion 12 d is provided with the through-holes 20 d and the balljoint 50, the first pins P1 may be inserted through whichever of thethrough-holes 20 d and/or the through-hole 60 of the ball joint 50depending on situations. This increases convenience.

Like an external fixation device 10 e shown in FIG. 23, there may be anarrangement that not only the ball joint 50 is attached to the secondholding portion 36 but also two ball joints 50 are attached to a frameportion 12 e. In this case, the frame portion 12 e includes asubstantially U-shaped frame main body 160; two support members 162 ontwo ends; and a support member 164 in a center. The frame main body 160has two hemispherical recesses 160 a; the support member 162 has asemicircular recess 162 a; and the support member 164 has two endregions each formed with a semicircular recess 164 a. The two ballportions 56 of the ball joints 50 are inserted into the two recesses 160a in the frame main body 160, and then the frame main body 160, thesupport member 164 and the two support members 162 are assembledtogether to surround exposed regions of the ball portions 56 with therecesses 162 a and the recess 164 a. Under this state, the frame mainbody 160, the support member 164 and the two support members 162 areintegrally assembled with unillustrated fasteners. Two surfaces of theframe main body 160 which are perpendicular to the third direction areformed with eight (four in each surface) screw holes 22. Otherarrangements are the same as in the external fixation device 10, sodescription therefor will not be repeated.

According to the external fixation device 10 e as described, freedom ofmovement of the knee joint A is further improved.

Like an external fixation device 10 f shown in FIG. 24, the ball joint50 may be attached to a frame portion 12 f, and a first holding portion14 f may be formed with two through-holes 166. In this case, the frameportion 12 f includes a substantially U-shaped frame main body 168, andtwo support members 170 as split halves. The frame main body 168includes first limiter portions 168 a, 168 b, and a connecting portion168 c which connects the first limiter portions 168 a, 168 b to eachother. The connecting portion 168 c of the frame main body 168 has ahemispherical recess 168 d, whereas the support members 170 havesemicircular recesses 170 a. The ball portion 56 of the ball joint 50 isinserted into the recess 168 d in the connecting portion 168 c, and thenthe frame main body 168 and the two support members 170 are assembledtogether to surround an exposed region of the ball portion 56 with thetwo recesses 170 a. Under this state, the frame main body 168 and thetwo support members 170 are integrally assembled with unillustratedfasteners. The first permanent magnet 32 is disposed on an inner surfaceof the first holding portion 14 f, whereas the second permanent magnet34 is disposed on an inner surface of the connecting portion 168 c. Twosurfaces of the frame portion 12 f which are perpendicular to the thirddirection are formed with eight (four in each surface) screw holes 22.With the above, the first pin P1 is inserted through each of the twothrough-holes 166 formed in the first holding portion 14 f, whereas thesecond pin P2 is inserted through the through-hole 60 of the ball joint50 which is attached to the frame portion 12 f. In this embodiment, theconnecting portion 168 c and the two support members 170 represent thesecond holding portion. Therefore, in the external fixation device 10 f,the first limiter portions 168 a, 168 b and the second holding portionare formed integrally with each other.

The external fixation device 10 f as described provides substantiallythe same advantages as offered by the external fixation device 10.

Like an external fixation device 10 g shown in FIG. 25, there may be anarrangement that two first limiter portions 172 a and 172 b are notconnected to each other by the first holding portion 36 a or the secondholding portion 36 b. The first holding portion 36 a and the secondholding portion 36 b have the same configuration as the second holdingportion 36 which is included in the external fixation device 10. Theexternal fixation device 10 g includes a first permanent magnet 32 and asecond permanent magnet 34 which are disposed with their same polesopposed to each other. The first holding portion 36 a is attached to asurface of the first permanent magnet 32 which faces away from theopposing surface 32 a, whereas the second holding portion 36 b isattached to a surface of the second permanent magnet 34 which faces awayfrom the opposing surface 34 a. Each of the first holding portion 36 aand the second holding portion 36 b is connected to a respective balljoint 50. The first permanent magnet 32, the second permanent magnet 34,the first holding portion 36 a and the second holding portion 36 bdescribed above are sandwiched from their sides (the second direction)by two plate-like first limiter portions 172 a, 172 b. Two surfaces ofthe first limiter portion 172 a which are perpendicular to the thirddirection are formed with four (two in each surface) screw holes 22.Likewise, two surfaces of the first limiter portion 172 b which areperpendicular to the third direction are formed with four (two in eachsurface) screw holes 22. The first pin P1 is inserted through the balljoint 50 on the first permanent magnet 32 side, whereas the second pinP2 is inserted through the ball joint 50 on the second permanent magnet34 side.

According to the external fixation device 10 g as described, freedom ofmovement of the knee joint A is improved further since each of the firstpermanent magnet 32 and the second permanent magnet 34 is movable in thefirst direction.

The shape of the permanent magnets is not limited to a rectangularparallelepiped. Like an external fixation device 10 h shown in FIG. 26,a first permanent magnet 174 which has a convexed opposing surface 174 aand a second permanent magnet 176 which has a concaved opposing surface176 a may be utilized. Other arrangements are the same as in theexternal fixation device 10, so description therefor will not berepeated.

According to the external fixation device 10 h as described, it ispossible to increase the area of opposing surfaces of the firstpermanent magnet 174 and the second permanent magnet 176, which makes itpossible to further increase the repulsion force.

Like an external fixation device 10 i shown in FIG. 27, both of firstlimiter portions 177 a and 177 b of the frame portion 12 i may beslanted in one direction. Accordingly, nonmagnetic platy members 178 a,178 b disposed on an inner side surface of the frame 12 i are alsoslanted. Other arrangements are the same as in the external fixationdevice 10, so description therefor will not be repeated.

According to the external fixation device 10 i as described, it ispossible to move the second permanent magnet 34 in a direction slantedfrom the first direction (oblique direction) with respect to the firstpermanent magnet 32.

Like an external fixation device 10 j shown in FIG. 28, part of a frameportion 12 j may be movable in a left-right direction. The frame portion12 j is structured like the frame portion 12 in FIG. 2 but in threepieces, i.e., a first frame 180, a second frame 182 and a third frame184. The first frame 180 and the second frame 182 are connected to eachother by a connecting member 186, whereas the first frame 180 and thethird frame 184 are connected to each other by a connecting member 186.Also, the first frame 180 has its inner side surfaces formed with twoplaty members 188 a; the second frame 182 has its inner side surfaceformed with a platy member 188 b; and the third frame 184 has its innerside surface formed with a platy member 188 c. The platy members 188 a,188 b and 188 c are nonmagnetic, preferably being formed of anonmagnetic stainless steel such as SUS304, aluminum, titanium, etc. Inthe external fixation device 10 j, second limiter portions are attachedindividually, i.e., for the first frame 180, for the second frame 182and the third frame 184. Other arrangements are the same as in theexternal fixation device 10, so description therefor will not berepeated.

According to the external fixation device 10 j as described, it ispossible to move the second permanent magnet 34 in the second direction(left-right direction).

Like an external fixation device 10 k shown in FIG. 29, a substantiallyC-shaped frame portion 12 k may be utilized. The frame portion 12 kincludes a first holding portion 190, and a pair of first limiterportions 192 a, 192 b extending like arcs from two ends of the firstholding portion 190. The frame portion 12 k is formed with a plurality(seven, in the present embodiment) of through-holes 20, and a plurality(eight, in the present embodiment (four in each surface which isperpendicular to the third direction)) of screw holes 22. The firstholding portion 190 has its inner surface, to which a rectangularparallelepiped first permanent magnet 194 is attached, whereas a secondpermanent magnet 196 is disposed to oppose the first permanent magnet194. The first permanent magnet 194 and the second permanent magnet 196are disposed with their same poles opposed to each other. The secondpermanent magnet 196 is held by a second holding portion 198 which ismovable in a gap between two end portions of the frame portion 12 k. Thesecond holding portion 198 includes a first support member 200 attachedto the second permanent magnet 196, and two second support members 202as halves. The first support member 200 has a hemispherical recess 200a, whereas each of the second support members 202 has a semicircularrecess 202 a. The ball portion 56 of the ball joint 50 is inserted intoa recess 200 a in the first support member 200, and then the firstsupport member 200 and the two second support members 202 are assembledtogether to surround an exposed region of the ball portion 56 with thetwo recesses 202 a. Under this state, the first support member 200 andthe two second support members 202 are integrally assembled withunillustrated fasteners. As described above, the ball joint 50 isconnected to the second holding portion 198.

According to the external fixation device 10 k as described, it ispossible to obtain a substantially cylindrical device, and it ispossible to dispose a plurality of through-holes 20 in an annularpattern in the frame portion 12 k. Therefore, it becomes possible toadjust a distance between the first pins P1 and the second pin P2 byselecting the through-holes 20 to insert the first pins P1.

Like an external fixation device 101 shown in FIG. 30, a through-hole206 may be formed in a second holding portion 204 which holds the secondpermanent magnet 34. In this case, the ball joint 50 is not attached tothe second holding portion 204, and the second pin P2 is insertedthrough the through-hole 206. Other arrangements are the same as in theexternal fixation device 10 e shown in FIG. 23, so description thereforwill not be repeated.

According to the external fixation device 101 as described,substantially the same advantages provided by the external fixationdevice 10 are obtained even if the ball joint 50 is not attached on thesecond pin P2 side, since the ball joint 50 is attached to the first pinP1 side.

Like an external fixation device 10 m shown in FIG. 31, it is acceptableeven if the ball joint 50 is not included. In the external fixationdevice 10 m, the first permanent magnet 32 is held by the frame portion12 shown in FIG. 2; the second permanent magnet 34 is held by a secondholding portion 204 shown in FIG. 30; the first pins P1 are insertedthrough the through-holes 20; and the second pin P2 is inserted througha through-hole 206.

As exemplified in the external fixation device 10 m, the presentinvention need not necessarily include the ball joint 50.

In the present invention, the number of ball joints attached to thefirst holding portion, and the number of through-holes formed in thefirst holding portion may be one or plural.

In the embodiment described above, as shown in FIG. 15 and in FIG. 19,the nuts 146 are used as stoppers when attaching the external fixationdevice and the pin fixture 100 to the first pins P1 and the second pinP2. However, the stoppers are not limited to this. As shown in FIG. 32for example, a stopper may be provided by a ring member 210 which has ascrew hole 208 penetrating in a radial direction and a bolt 212 threadedthrough the screw hole 208. In this case, at least one of the first pinand the second pin is provided by a pin Pa as shown in FIG. 33. The pinPa is rod-like, and has flat surfaces 214 on its two end portions. Theflat surfaces 214 are wider than the place where the external fixationdevice, the pin fixture 100 and the ring member 210 are attached. Thus,the ring member 210 is movable axially of the pin Pa even if the bolt212 threaded through the ring member 210 is in contact with the flatsurface 214.

Since the ring member 210 attached to the pin Pa is movable axially ofthe pin Pa as described, the external fixation device and the pinfixture 10 which are attached to the pin Pa are movable axially of thepin Pa, making it possible to move the knee joint A more freely.

As shown in FIG. 34, the first pins and the second pin may be providedby a pin Pb which has a head portion 216.

In regard to the external fixation device 10, there may be arrangementsas shown in FIG. 3, in alternate long and short dash lines, that theframe portion 12 is formed with the screw holes 218 which providescommunication between an outer surface of the frame portion 12 and thethrough-holes 20; and as shown in FIG. 8, in alternate long and shortdash lines, the second shaft portion 54 of the ball joint 50 is formedwith a screw hole 220 which provides communication between an outersurface of the tube-like portion 62 and the through-hole 60. Further, inregard to the pin fixture 100, there may be arrangements that as shownin FIG. 12, in alternate long and short dash lines, the fixture mainbody 102 is formed with a screw hole 222 which provides communicationbetween an outer surface of the thick portion 108 and the through-hole118; as shown in FIG. 13, in alternate long and short dash lines, thefirst connecting portion 104 is formed with a screw hole 224 whichprovides communication between an outer surface of the thick portion 124and the through-hole 128; and as shown in FIG. 14, in alternate long andshort dash lines, the second connecting portion 106 is formed with ascrew hole 226 which provides communication between an outer surface ofthe thick portion 132 and the through-hole 136.

In these cases, it is possible to fix the first pins P1 and the secondpin P2 by threading the bolt 212 shown in FIG. 32 into the screw holes218, 220, 222, 224 and 226, without using the nuts 146 or the ringmembers 210.

Further, the first pins P1 and the second pin P2 may have their endportions provided with resin caps to prevent the external fixationdevice and the pin fixture 100 from coming off the first pins P1 and thesecond pin P2.

The first permanent magnet 32 b and the second permanent magnet 34 b asshown in FIG. 20 may also be used in the external fixation device shownin FIG. 21 through FIG. 31. Also, the first permanent magnet and thesecond permanent magnet may be disposed to have their S poles to opposeto each other, with their respective N poles on the outer side.

In the external fixation device 10 a shown in FIG. 17, the slantedsleeve 148 may be replaced with an ordinary sleeve 228 as shown in FIG.35. The sleeve 228 has a through-hole 230, which is not slanted withrespect to an axis direction of the sleeve 228. The sleeve 228 isnonmagnetic, preferably being formed of a nonmagnetic stainless steelsuch as SUS304, aluminum, titanium, etc. Also, the slanted sleeve 148may be replaced with a hollow tube-like member which has flexibilitylike resin or rubber.

A plurality of slanted sleeves may be used in one external fixationdevice. Also, the slanted sleeve may be fitted into a through-holeformed in the second holding portion.

The first holding portion and the pair of first limiter portions in theframe portion may be assembled together with fasteners such as bolts.

The present invention is applicable not only to knee joints but also anyother joints such as ankle joints, hip joints, hand joint, elbow jointsand finger joints. In these cases, locations and numbers ofthrough-holes and ball joints may be modified depending on the bodypart.

The present invention being thus far described in terms of preferredembodiments, it is obvious that these may be varied in many ways withinthe scope and the spirit of the present invention. The scope of thepresent invention is only limited by the accompanied claims.

REFERENCE SIGNS LIST

-   10, 10 a through 10 m External fixation devices-   12, 12 a, 12 d, 12 e, 12 f, 12 i, 12 j, 12 k Frame portions-   14, 14 f, 36 a, 190 First holding portions-   16 a, 16 b, 168 a, 168 b, 172 a, 172 b, 177 a, 177 b, 192 a, 192 b    First limiter portions-   20, 20 a, 20 d, 60, 74, 74 a, 80, 80 a, 118, 128, 130, 136, 138,    154, 166, 206, 230 Through-holes-   32, 32 b, 174, 194 First permanent magnets-   32 a, 34 a, 174 a, 176 a Opposing surfaces-   34, 34 b, 176, 196 Second permanent magnets-   36, 36 b, 198, 204 Second holding portions-   50, 50 a Ball joints-   66, 66 a Second limiter portions-   100 Pin fixture-   102 Fixture main body-   104 First connecting portion-   106 Second connecting portion-   140, 144, 212 Bolts-   146 Nut-   148 Slanted sleeve-   210 Ring member-   A Knee joint-   B First bone portion-   C Second bone portion-   P1 First pin-   P2 Second pin-   Pa, Pb Pins-   S Fixation device set-   X First direction-   Y Second direction-   Z Third direction

1. An external fixation device for keeping a first bone portion and asecond bone portion separated from each other in a joint, by attachingto a first pin which penetrates the first bone portion and to a secondpin which penetrates the second bone portion, the device comprising: afirst permanent magnet and a second permanent magnet which are opposedto each other, with their same poles facing each other; a first holdingportion which is disposed on a surface of the first permanent magnet, ona side facing away from a surface opposing to the second permanentmagnet, and is attached to the first pin; a second holding portion whichis disposed on a surface of the second permanent magnet, on a sidefacing away from a surface opposing to the first permanent magnet, andis attached to the second pin; and a pair of first limiter portionswhich allow movement of the first permanent magnet and the secondpermanent magnet in a first direction defined as a direction of theirrepulsion force by sandwiching the first permanent magnet and the secondpermanent magnet from a second direction defined as a directionperpendicular to the first direction, and limit movement thereof in thesecond direction.
 2. The external fixation device according to claim 1,further comprising a second limiter portion disposed to connect the pairof first limiter portions to each other to limit movement of the firstpermanent magnet and the second permanent magnet in a third directiondefined as a direction perpendicular to both of the first direction andthe second direction.
 3. The external fixation device according to claim2, wherein the second limiter portion includes a magnetic member.
 4. Theexternal fixation device according to claim 1, further comprising a balljoint for attaching at least one of the first holding portion and thesecond holding portion to a corresponding one of the first pin and thesecond pin.
 5. The external fixation device according to claim 4,wherein the second holding portion is connected to the ball joint,whereas the first holding portion has a through-hole for insertion ofthe first pin.
 6. The external fixation device according to claim 1,wherein at least one of the first holding portion and the second holdingportion has a through-hole for insertion of the corresponding one of thefirst pin and the second pin.
 7. The external fixation device accordingto claim 5, further comprising a slanted sleeve fitted into thethrough-hole.
 8. The external fixation device according to claim 1,wherein the pair of first limiter portions and the first holding portionare integral with each other.
 9. The external fixation device accordingto claim 1, wherein each of the first permanent magnet and the secondpermanent magnet is rectangular parallelepiped.
 10. A fixation deviceset comprising: the external fixation device according to claim 1, forattaching to the first pin and the second pin on their common oneend-side; and a pin fixture for attaching to the first pin and thesecond pin on their common another end-side; wherein the pin fixtureincludes: a fixture main body; a first connecting portion for connectingthe fixture main body to the first pin; and a second connecting portionfor connecting the fixture main body to the second pin.
 11. The fixationdevice set according to claim 10, wherein the first connecting portionis pivotable with respect to the fixture main body, whereas the secondconnecting portion is linearly movable with respect to the fixture mainbody.